The goals of this Core are to: (1) Measure small molecules (primarily amino acids and biogenic amines) of central importance to brain chemistry. (2) Assay stable isotope enrichment with mass spectrometry in order to perform kinetic studies of metabolic flux, both in vitro and in people with developmental disabilifies. (3) Idenfify and characterize pepfides and proteins that are important to neurologic function. (4) Perform cell-based assays of physiologic processes that are important to brain funcfion, including assays of Ca2+, calpain, caspase and ROS; (5) Assist users with regard to experimental design and data interpretation. The rationale for the core is that neurochemical derangements occur in many developmental disabilifies, including metabolic diseases, hypoxic injury, epilepsy, neurotoxicity, etc.